In a letter to Internal Revenue Service Commissioner Charles Rettig, U.S. Sens. Chuck Grassley, R-Iowa, and Mike Crapo, R-Idaho, with Republican members of the Finance Committee, called for continued oversight of IRS data security practices following ProPublica’s publishing of tax return data. With the unknown source of data, the lawmakers said the IRS's ability to safeguard information "also remains unknown." They added if information was “leaked or hacked from the IRS” it could indicate an “ongoing and persistent problem” in the agency’s ability to protect data.